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Tuesday, October 9, 2007

INTRODUCTION — Asthma is a common lung disease affecting millions of people worldwide. It is caused by narrowing of the small airways (tubes) in the lungs. This narrowing is usually reversible, but may occasionally become permanent over time. Many different genetic and environmental factors play a role in causing asthma. Symptoms of asthma include wheezing, coughing, chest tightness, and shortness of breath. These symptoms tend to come and go, and are related to the degree of airway narrowing in the lungs.

A number of different medicines are useful in treating asthma, but not all asthma medicines are appropriate for every patient. Medicines used to treat asthma vary in cost, method of delivery, and potential side effects. Patients are affected differently by asthma, so patients, doctors, and other health care professionals must work together to develop an individualized treatment plan.

The purpose of asthma treatment is to manage the disease in order to live as normal a life as possible. This requires being well educated about the disease and being an active player in managing it. Most people with asthma are successful in controlling the disease.

The severity of asthma is an important factor in determining an asthma treatment plan. Asthma is generally classified as mild, moderate, or severe based on history of the disease, studies of lung function, and medication use. A patient's history includes frequency and severity of symptoms that occur with activities of daily living, such as walking, running, climbing stairs, carrying packages up stairs, and sleeping. The majority of people with asthma have a mild case (show table 1).

Successful management of asthma involves four components: Understanding the disease and how to treat it Controlling things that trigger asthma Regularly monitoring symptoms and lung function Medication

CONTROLLING ASTHMA TRIGGERS — The factors that set off and exacerbate asthma symptoms are called "triggers." Identifying and avoiding asthma triggers is essential in preventing asthma flare-ups. Common triggers generally fall into several categories: Allergens (including dust and animal fur) Respiratory infections Irritants (such as smoke or chemicals) Physical activity Emotional stress Menstrual cycle in women

A small number of patients will develop asthmatic symptoms after exposure to aspirin or other nonsteroidal antiinflammatory medications, like ibuprofen or naproxen. (See "Patient information: Trigger avoidance in asthma").

After identifying potential asthma triggers, a patient and their clinician should develop a plan to deal with the triggers. There are three main options: Avoid the trigger entirely (eg, if allergic to animals, do not own pets, or if asthma is triggered by dust, have someone else do the house cleaning) Limit exposure to the trigger if it cannot be completely avoided (eg, move to another seat if someone with strong perfume is seated nearby) Take an extra dose of bronchodilator medication before exposure to a trigger. Talk with a healthcare provider before using this approach; it should only be used if the first two options are not possible. Be careful not to use more than twice the amount of medication normally used.

MONITORING SYMPTOMS AND LUNG FUNCTION — Successful management of asthma relies on a patient's ability to monitor their condition regularly. This is done by recording the frequency and severity of symptoms (such as wheezing, coughing, and shortness of breath) and by obtaining numerical measurements of lung function, such as peak expiratory flow rates (PEFRs).

Peak expiratory flow rate — PEFR measures the rate at which a patient can exhale. This rate is dependent on the degree of airway narrowing. PEFR monitoring can provide firm data that can be used to make treatment decisions. The National Asthma Education and Prevention Program recommends that people with moderate to severe persistent asthma use a peak flow meter daily to monitor their lung function. PEFR measurement can be used to monitor lung function and response to treatment, assess the severity of asthma attacks, and guide decisions regarding treatment.

Peak flow meters are inexpensive and easy to use. PEFR is usually measured when getting up in the morning and before going to bed at night. For more information, see "Patient Information: How to use a peak flow meter".

Asthma diary — Using an asthma diary to record daily peak flow readings and asthma symptoms can help patients to identify a cause-and-effect relationship between exposure to certain asthma triggers, decreases in peak flow, and exacerbations of asthma. The diary can also help track medication use (show figure 1).

TREATMENT — Medication is the main form of treatment for most people in managing asthma. The medications used vary according to the type and severity of asthma. An individual's asthma treatment plan must constantly be adjusted because the severity of the disorder changes over time. As symptoms improve, medication should be reduced. As symptoms worsen, medication should be increased.

Mild intermittent asthma — People with mild intermittent asthma are defined in part as those who have: Symptoms of asthma occurring two or fewer times per week Two or fewer awakenings during the night per month Peak flow measurements when asymptomatic that are consistently within the normal range (ie, PEFR >80 percent of predicted normal)

In addition, a person with asthma that is triggered only during vigorous exercise (exercise-induced asthma) might fit into this category even if exercising more than twice per week. Others in whom asthmatic symptoms arise only under certain infrequently occurring circumstances (eg, when exposed to a cat or during some viral respiratory tract infections) are also considered to have mild intermittent asthma.

Bronchodilators — People with mild intermittent asthma have the mildest form of asthma and require treatment with bronchodilators (called beta agonists) only occasionally. Bronchodilators are medicines that help open the narrowed airways of patients with asthma. Although patients with mild intermittent asthma can take bronchodilators on a regularly scheduled basis without harmful effects, there is no advantage over taking them only when needed.

The preferred way of taking medication for people with mild intermittent asthma is using an inhaler. This method allows the medication to take effect rapidly with maximum strength and minimal side effects. People who can predict triggers of asthma symptoms (eg, exercise-induced symptoms) are encouraged to use their inhalers approximately 10 minutes before exposure in order to prevent symptoms from occurring. Inhaled beta agonists can also relieve symptoms after they have started. (See "Patient Information: Metered dose inhaler techniques" for information on how to use an inhaler).

Some people experience tremulousness, palpitations, and/or anxiety from inhaled beta agonists. Using a single inhalation of the medication for prevention or relief of symptoms rather than the usual two puffs may alleviate these reactions with a minimal decrease in benefit.

Mast cell stabilizers — Mast cell stabilizing medications, such as cromolyn (Intal®) and nedocromil (Tilade®), are alternate medications for prevention of exercise-induced symptoms. Two inhalations of either medication taken about 10 to 20 minutes before exercising can provide effective preventive treatment with no side effects. However, they cannot relieve symptoms that have already started. These medications provide additive protection when used with a beta agonist before exercising.

Mild persistent asthma — People with mild persistent asthma have symptoms regularly but not every day. Although they have days with some limitation in their activities, they are typically not restricted. They may be awakened from sleep three to four times a month by symptoms but most nights they sleep well. Lung function is usually normal between episodes but becomes abnormal during an asthma attack.

It is useful to start regular treatment with antiinflammatory medications when a person has one of the following: Symptoms requiring relief with an inhaled bronchodilator more than twice a week Awakenings during the night more often than twice a month Changes in PEFR of more than 20 percent

Antiinflammatory medications — Regular treatment with antiinflammatory medications reduces the frequency of symptoms (and the need for inhaled bronchodilators for symptom relief), improves quality of life, and decreases the risk of serious exacerbations. By reducing over-responsiveness of the bronchial tubes, regular antiinflammatory treatment change the basic condition of the airways that causes asthma and reduces a patient's exaggerated sensitivity to asthma triggers.

For adults, the most frequently recommended type of antiinflammatory medication is an inhaled corticosteroid. It is usually taken twice a day. People who are taking antiinflammatory medication regularly should continue to use their inhaled bronchodilator as needed for relief of symptoms and before exposure to their asthma triggers. Side effects — The most common side effect from this type of medication is oral candidiasis (thrush). This complication is infrequent when inhaled corticosteroids are taken with a spacer (which helps to deliver medication to the lungs rather than the mouth) and if the patient rinses their mouth immediately after inhalation.

Hoarse voice and sore throat (without thrush) are less common side effects that usually resolve quickly after temporarily stopping the medication. If inhalation causes coughing with each use, changing to a different steroid preparation may relieve the problem.

Leukotriene blockers — A separate category of medications called leukotriene blockers provides an alternative to inhaled steroids in patients with mild persistent asthma. They are in pill form, are taken by mouth once or twice daily, and have very few side effects. However, compared to inhaled corticosteroids they are somewhat less effective in controlling asthma and are more expensive.

Moderate persistent asthma — The presence of any of the following is an indication of moderate asthma: Daily symptoms Daily need for bronchodilator medications Asthma attacks that interfere with daily activities Awakening during the night more than once per week PEFR 60 to 80 percent of normal

Controller medications — Patients who have moderate persistent asthma often need to use medicines on a daily basis to keep their asthma under control. For these patients, controller medicines are important, and should be used regularly even if there are no symptoms of active asthma. Controller medicines work over time to decrease the amount of inflammation (or narrowing) of the small airways. Some controller medicines are delivered by inhaler while others are taken by mouth. Controller medicines include long-acting bronchodilators, inhaled or oral steroids, and oral leukotriene modifiers like montelukast (Singulair®)

Many people whose asthma is poorly controlled on low doses of inhaled corticosteroids improve when the dose is raised. If they have moderate persistent asthma, they should use a dose at the high end of the medium dose range. They should also use quick-acting beta agonists for relief of sudden onset symptoms.

If symptoms continue several weeks after starting inhaled corticosteroids at the high end of the medium dose range, a second controller medication should be added. These include salmeterol (contained in Advair®), montelukast (Singulair®) zafirlukast (Accolate®) or sustained release theophylline. Side effects — As the dose of inhaled corticosteroids is increased, the likelihood of systemic absorption and the chance for significant side effects from long-term use increase. Side effects from long-term use may include: Increased pressure in the eye Cataracts Growth retardation Increased bone loss

The risk of these complications is far less with inhaled corticosteroids than with oral corticosteroids. Nevertheless, in patients with moderate or severe asthma whose disease has been well controlled with high-dose inhaled corticosteroids, every effort should be made to reduce the dose to as low as possible while maintaining good asthma control and minimizing the risk of exacerbations.

Severe asthma — The following are indications of severe chronic asthma: Frequent asthma exacerbations as a result of minor exposures to viral illnesses, allergens, exercise, or air pollutants Awakenings from sleep four to seven nights per week PEFR below 60 percent of predicted normal Inability to achieve normal lung function despite chronic treatment with multiple medications, including inhaled steroids at moderate to high dose, or continuous, every other day, or multiple short courses of oral steroids.

People with severe asthma usually require multiple controller medications and bronchodilator medications on a regular basis. If they cannot achieve symptom control with two controller medications, they are likely to require the addition of oral corticosteroids or high-dose inhaled corticosteroids. Consultation with an asthma specialist is warranted in cases of severe asthma.

ASTHMA IN PREGNANCY — Asthma is the most common condition that affects the lungs during pregnancy. About 4 percent of pregnant women have asthma. With good asthma treatment during pregnancy, most women can breathe easily, have a normal pregnancy, and give birth to a healthy baby.

Before becoming pregnant, women with asthma should learn as much as they can about the condition and talk with their doctors about asthma treatment during pregnancy. More information about asthma during pregnancy is presented separately. (See "Patient Information: Pregnancy and asthma").

WHERE TO GET MORE INFORMATION — Your healthcare provider is the best source of information for questions and concerns related to your medical problem. Because no two patients are exactly alike and recommendations can vary from one person to another, it is important to seek guidance from a provider who is familiar with your individual situation.

This discussion will be updated as needed every four months on our web site (www.patients.uptodate.com). Additional topics as well as selected discussions written for healthcare professionals are also available for those who would like more detailed information.

A number of web sites have information about medical problems and treatments, although it can be difficult to know which sites are reputable. Information provided by the National Institutes of Health, national medical societies and some other well-established organizations are often reliable sources of information, although the frequency with which they are updated is variable. The National Library of Medicine

(www.aaaai.org/patients.stm)American College of Allergy, Asthma, and Immunology

(www.acaai.org/public/)

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Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. Worldwide variation in prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema: ISAAC. The International Study of Asthma and Allergies in Childhood (ISAAC) Steering Committee. Lancet 1998; 351:1225.2. National Asthma Education Program Expert Panel. Guidelines for the diagnosis and management of asthma. US Department of Health and Human Services, National Institutes of Health, Bethesda, 1997.3. National Asthma Education and Prevention Program Expert Panel Executive Summary Report: Guidelines for the Diagnosis and Management of Asthma - Update on Selected Topics 2002. National Institutes of Health, National Heart, Lung, and Blood Institute, Publication No. 02-5075, 2002. Full text available online: www.nhlbi.nih.gov/guidelines/asthma/asthgdln.pdf (Accessed 3/7/05).